Author: Sofia Prado-Irwin Page 2 of 4

On October 16, 2017

Anolis vermiculatus, by Raimundo López-Silvero Martínez

Another year, another field season (or seasons) come and gone, and now it’s time to share the great anoles we’ve seen! Get ready for the Anole Annals Photo Contest: 2017 Edition.

As in previous years, the Anole Annals team wants to see your best anole photographs for our 2018 calendar.

Here’s how it works: anyone who wants to participate will submit their favorite photos. The editors of Anole Annals will choose a set of 30-40 finalists from that initial pool. We’ll then put those photos up for a vote on this here blog, and the 12 winning photos will be chose by readers of Anole Annals, as well as a panel of anole photography experts. The grand prize winner and runner-up will have his/her photo featured on the front cover of the 2017 Anole Annals calendar, second place winner will have his/her photo featured on the back cover, and they’ll both win a free calendar!

Before we move on, I’d like to issue a correction from last year’s calendar – due to an unfortunate email miscommunication, we accidentally attributed several photos to the wrong photographer. By the time we realized our mistake, the calendar was already in print. We would like to sincerely apologize to Raimundo López-Silvero Martínez and Rosario Basail, whose photos, Anolis vermiculatus (September) and Anolis garridoi (April) respectively, we mis-credited. But please, take a look and appreciate them here! We will be sure to be more careful this year.

Anolis garridoi, by Rosario Basail

Back to business. The rules: submit your photos (as many as you’d like) as email attachments to anoleannalsphotos@gmail.com. To make sure that your submissions arrive, please send an accompanying email without any attachments to confirm that we’ve received them. Photos must be at least 150 dpi and print to a size of 11 x 17 inches. If you are unsure how to resize your images, the simplest thing to do is to submit the raw image files produced by your digital camera (or if you must, a high quality scan of a printed image). If you elect to alter your own images, don’t forget that it’s always better to resize than to resample. Images with watermarks or other digital alterations that extend beyond color correction, sharpening and other basic editing will not be accepted. We are not going to deal with formal copyright law and ask only your permission to use your image for the calendar and related content on Anole Annals (more specifically, by submitting your photos, you are agreeing to allow us to use them in the calendar). We, in turn, agree that your images will never be used without attribution and that we will not profit financially from their use (the small amount of royalties we receive are used to purchase calendars for the winners). Please only submit photos you’ve taken yourself, not from other photographers–by submitting photos, you are declaring that you are the photographer and have the authority to allow the photograph to be used in the calendar if it is chosen.

Good luck, and we look forward to seeing your photos!

Evolution 2017: Experimentally Testing Perch Choice in Urban and Forest Lizards

On June 28, 2017

Cities and urban areas are expanding rapidly around the world, altering the environment and creating very different ecological and selective pressures for organisms that live in urban habitats. A few of the most striking differences between urban and natural habitats are higher temperatures and a huge increase in artificial substrates like the walls of buildings. These artificial substrates (e.g., metal, concrete) are not only significantly smoother than natural (i.e., trees) substrates, but also absorb, retain, and radiate heat differently. Consequently, organisms may alter their behavior to better deal with these and other challenges of city life. Since anoles cannot internally regulate their temperature, behavioral shifts may be driven by perch substrate properties, temperature, or some interaction of the two.

Kevin Aviles-Rodriguez (U. Mass. Boston) addressed this question in urban Anolis cristatellus in San Juan, Puerto Rico. He created experimental enclosures in which each wall was a different substrate: wood, plastic, painted cement, and metal. He placed individual lizards into the enclosures and observed which wall they were perched on throughout the day. He also recorded the temperature of each wall, to determine how perch temperature of each substrate type influenced perch choice. Aviles-Rodriguez conducted this experiment in both urban and forest populations, and predicted that urban lizards would use artificial substrates more readily than forest lizards.

Interestingly, he did not find that to be the case – lizards from both urban and forest habitats used bark much more than any other surface. However, when lizards did use artificial substrates, they tended to use metal and cement when these perches were cooler, suggesting that perch temperature is a factor in perch choice. Aviles-Rodriguez plans to test these hypotheses more thoroughly by conducting additional experiments across more urban replicates to see if the same pattern emerges. He also plans to experimentally control the temperatures of different perch substrates in his enclosures to see whether lizard choices are primarily driven by perch substrate or temperature.

Evolution 2017: Genetics of Ecologically Divergent Anoles

On June 27, 2017

Anolis distichus is well-known in the anole world for the high degree of ecomorphological variation within the species, especially in dewlap color. In fact, there are 18 described subspecies! While there is some gene flow between various subspecies and populations, the phenotypic differences are maintained, which suggests strong selection. But the fine-scale genetic structure underlying these traits is not well understood. Anthony Geneva and colleagues decided to explore the genomic basis of adaptive divergence in a well-described hybrid zone between two A. distichus subspecies. The first, A. d. ignigularus, has a white dewlap, and occupies a dry forest habitat while the second, A. d. ravitergum, has a red dewlap and inhabits a wetter habitat. The two subspecies occur along a transect from dry to wet, and they hybridize in a narrow contact zone in the middle. These two subspecies provide a great system to explore the link between adaptive and genetic divergence.

Anolis distichus. Photo by Rich Glor

Geneva sequenced individuals using RNASeq across an environmental transect from wet to dry, including allopatric and sympatric populations of both species. He examined levels of divergence and introgression to explore which genomic loci might be the basis for the ecological adaptive divergence between these two species. He found a suite of candidate genes that differ between the two subspecies, as well as several that show signs of introgression between the two. Interestingly, several of the divergent genes are involved in two traits that likely are impacted the environment – insulin signaling, which may relate to metabolic differences between hot and cool climates, and vision, which may relate to differences in light availability and signal efficiency. Most of the introgressed genes, on the other hand, relate to conserved pathways, suggesting that these genes play similar roles in both subspecies.

Adpative divergence in anoles has been a topic of interest for a long time, and Geneva’s study provides and a valuable insight to the genetic basis of this interesting phenomenon.

Evolution 2017: Sexually Antagonistic Selection in Juvenile and Adult Anoles

On June 27, 2017

Sexually antagonistic selection occurs when traits are beneficial for one sex, but detrimental to the other. This commonly occurs in species with sexual dimorphism, such that one trait is positively correlated with fitness in one sex, and negatively correlated with fitness in another. But in many organisms, the sexes do not become dimorphic until maturity – that is to say, juveniles all look pretty much alike, even when adults show clear differences between males and females. Which leads to the question: how does sexually antagonistic selection change over an organisms’ lifespan? Research from studies of Drosophila flies suggests that this is the case, but the question hasn’t been well-studied in vertebrates.

Everyone’s favorite anole, Anolis sagrei

Until now. In his Evolution talk, Aaron Reedy (University of Virginia) described his work testing whether sexually antagonistic selection changes over ontogeny using our favorite workhorse of evolutionary ecology, the brown anole (A. sagrei). Anolis sagrei are sexually dimorphic, with adult male body sizes up to 30% larger than females, but juveniles are monomorphic. Reedy and colleagues sampled A. sagrei on several small islands in a Florida watershed four times a year, capturing thousands of adults and juveniles. They measured the body size of all lizards captured, and combined this morphological data with survivorship data to determine how selection was acting on body size in adults and juveniles.

They predicted that juvenile males and females would experience concordant selection, while adult males and females would experience antagonistic selection. And this is exactly what they found: for juveniles, body size was correlated with survival in the same way between sexes. But in adults, this was not the case. In the first year of sampling, there was no selection on body size for adult females, but positive selection for males, such that bigger males survived better. Interestingly, during the second year of sampling, the relationship flipped – females experienced positive selection on body size, and males experienced negative selection. The reasons for this shift are uncertain, but the main point is clear – sexually antagonistic selection does indeed change over ontogeny. Reedy et al. are planning to follow up this great new research by expanding their study to look at more islands and more traits to get at the finer points of these selective differences, so stay tuned!

Evolution 2017: Genetic Constraints in the Anolis Adaptive Radiation

On June 26, 2017

As a lineage splits and diversifies, species’ traits diverge in different ways. For example, as anoles diversified in the Caribbean, trunk-ground anoles’ bodies become muscular and stocky, trunk-crown anoles’ heads become long and thin, and grass anoles’ tails become long and slender. This process of adaptation to different environments seems simple and intuitive, but the evolution of traits is not so simple.

Most traits don’t evolve independently – changes in one trait are often correlated with changes in another trait, which can constrain a species’ response to selection. This correlation between traits is represented by the genetic variance-covariance matrix (G matrix). The size, shape, and orientation of the G matrix determine the speed and direction of morphological change, and defines the “line of least genetic resistance” along which a species can evolve. But of course, as species diverge and their traits shift, the correlations between these traits themselves may not stay constant – that is to say, the G-matrix itself can evolve. Which means that G represents both a constraint on evolutionary change, as well as a product of evolution itself. So does the G matrix evolve along with species divergence, or does it limit morphological evolution?

In his talk at Evolution 2017, Joel McGlothlin (Virginia Tech) described his efforts to address these question in anoles. As a poster child of adaptive radiation, Anolis provides an excellent opportunity to explore the dynamics of G matrix evolution and evolutionary constraint. To that end, McGlothlin and colleagues estimated G matrices for seven anole species (no easy task), including representatives from three ecomorph categories. He laid out the following question: has the G matrix evolved as Anolis diversified? Or do we see a signature of constraint conserved across anoles?

First, McGlothlin and colleagues found that the G matrix has indeed evolved in the course of Anolis diversification: the shape, orientation, and size of the G matrix was different for each species studied. More closely related species had more similar G matrices, and there was a weak link between ecomorph and G matrix structure, but overall, G was clearly different across the seven anole species. This suggests that trait correlations (and therefore species’ potential responses to selection) are not necessarily constant across the anole radation.

However, despite this overall divergence, one important aspect of the G matrix – its orientation – was similar across all anole species sampled. This suggests that the line of least genetic resistance has remained constant throughout the diversification of anole ecomorphs, and is deeply conserved. So even though individual species’ trait correlations have changed as anoles have diverged, the signature of morphological constraint has persisted. The study provides a fascinating illustration of the complexity of morphological evolution, and provides a fresh new link between micro- and macro- evolutionary processes in Anolis lizards.

Calcium Storage in Anoles

On May 14, 2017

Enlarged endolymphatic glands in two A. lemurinus museum specimens

I’ve been looking through a lot of anole museum specimens lately, and I’ve noticed that many of them have pretty pronounced endolymphatic glands, which made me curious about their prevalence and function in anoles generally.

Endolymphatic glands serve as calcium reserves, and are present in many animals, including a number of reptile and amphibian clades. According to Etheridge (1959), these glands are present in anoles and a few of their close relatives (e.g. Polychrus), but not in any other Iguanians. But it looks like most of the research on their function (in reptiles) has focused on geckos. In geckos, the size of the glands has been shown to fluctuate in response to both stress and reproductive activity, supporting the idea that the stored calcium is used in egg production, both for the yolk and the shell (Brown et al. 1996, Lamb et al. 2017). However, in anoles and geckos, these glands are present in both males and females, so their function isn’t limited to providing calcium for eggs (Etheridge 1959, Bauer 1989, Lamb et al. 2017).

But I haven’t found much information on these glands in anoles. I personally haven’t noticed them in the wild, but so far I’ve found very pronounced glands in 13/66 museum specimens, and some of them are really striking (see photos)! So I’m curious to hear, how often do you other anole-ologists see these enlarged glands? Is there any other literature about their prevalence, seasonality, or function in anoles that I’ve overlooked? Seems like we might be lagging behind the gecko crowd on this topic!

Citations:

Bauer A (1989) Extracranial Endolymphatic Sacs in Eurydactylodes ( Reptilia : Gekkonidae), with Comments on Endolymphatic Function in Lizards. J Herpetol 23:172–175.

Brown SG, Jensen K, DeVerse HA (1996) The Relationship Between Calcium Gland Size, Fecunduty and Social Behavior in the Unisexual Gecks Lepidactyluse Lugubris and Hemidactylus Garnotii. Int J Comp Psychol. doi: 10.5811/westjem.2011.5.6700

Etheridge R (1959) The relationships of the anoles (Reptilia: Sauria: Iguanidae) an interpretation based on skeletal morphology.

Lamb AD, Watkins-colwell GJ, Moore JA, et al (2017) Endolymphatic Sac Use and Reproductive Activity in the Lesser Antilles Endemic Gecko Gonatodes antillensis (Gekkota: Sphaerodactylidae). Bull Peabody Museum Nat Hist 58:17–29.

Anole Annals 2017 Calendars Are Here!

On December 9, 2016

Thank you to all who sent in photos for our contest; we received a total of 101 submissions! We’ve tallied the results and consulted our panel of experts, and are ready to announce the winners for Anoles 2017. The grand prize winner is the photo above, Anolis equestris potior, taken by Jesús Reina Carvajal. The second place winner is below, Anolis aquaticus, taken by Lindsey Swierk. Congratulations!

The rest of the winners can be seen in the 2017 calendar here! Click the link to order your calendar, just in time for the holidays. Congratulations to all the winners, and thank you again to everyone who participated!

Happy holidays! Can’t wait to see the submissions next year!

Anole Photo Contest 2016 – Time to Vote!

On November 16, 2016

Thank you to everyone who submitted photos for the Anole Annals 2016 calendar contest, we received so many great submissions! We’ve narrowed it down to the top 30, and now it’s time to vote! Choose your 5 favorites in the poll below. You can click on the thumbnail to view full-size images. You have 5 days to vote – poll closes on Monday at midnight (11/21).

Reminder: Submit Photos for Anole Photo Contest 2016!

On October 30, 2016